I have been rereading the excellent article by Todd Keister and James McAndrews “Why Are Banks Holding So Many Excess Reserves”, published in the Volume 15, Number 8 of Current Issues (December 2009).
http://www.newyorkfed.org/research/current_issues/ci15-8.pdf
As QE 3 is winding up, it may provide some useful insights into how QE actually worked, why it totally failed to contribute to inflation, and why it was not very effective at providing economic stimulus.
Enjoy.